1. Field of the Invention
Implementations of various technologies described herein generally relate to methods and systems for synchronizing a seismic data acquisition network.
2. Description of the Related Art
The following descriptions and examples are not admitted to be prior art by virtue of their inclusion within this section.
Typically, seismic surveys may be performed for the purpose of geotechnical projects, such as hydrocarbon exploration. To perform the seismic survey, a survey system may be deployed that produces and records seismic data about a survey area.
The survey system includes a seismic data acquisition network. Typically, the network exchanges communications between sensors, concentrators and a recording truck. The sensors and concentrators are also referred to herein as nodes. Each of the nodes may include a real-time clock that provides the times of survey events which are used for seismic data processing.
A real-time clock (RTC) is a computer clock (most often in the form of an integrated circuit) that keeps track of the local time. Although the term RTC often refers to the devices in personal computers, RTCs are present in almost any electronic device which keeps time.
Typically, RTCs drift, which may introduce timing errors to the seismic data processing. As such, it may be desirable to synchronize the RTCs in the network. A reference clock may be used for the synchronization. The reference clock is a clock with a pre-defined precision. By synchronizing the RTCs with the reference clock, timing errors may be limited to a range that is acceptable for the seismic data processing.
Usually, the reference clock is placed on a recording truck. The recording truck may periodically send packets of data containing the reference clock time to some of the nodes. These nodes may adjust the values of their RTCs according to the time value of the reference clock included in the data packets. Now synchronized, these nodes may then synchronize other nodes in the same fashion.
The relationship between the nodes may be described by labeling nodes as masters and slaves. It should be noted that a single node may be both a master and a slave. For example, a node A may be a slave to node B, but a master to node C. In such a case, node A adjusts node A's RTC to the time value received from node B. Similarly, node C adjusts node C's RTC to the time value received from node A.